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Ashutosh et al. European Journal of Pharmaceutical and Medical Research
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EFFECT OF EXTRA AMOUNT OF HEPARIN IN SYRINGE AND ITS EFFECT ON
ARTERIAL BLOOD GAS ANALYSIS
Ashutosh Kumar
1 , Supriya Kushwah
2 and Shambhavi Sahay
3
1 Post Graduate, Department of Anaesthesia, A.J. Institute of Medical Sciences and Research Centre, Mangalore.
2 Assistant Professor, Department of Pediatrics, Yenepoya Medical College, Mangalore.
3 Senior Resident, Department of Pediatrics, S.M.S., Jaipur.
Article Received on 20/09/2015 Article Revised on 10/10/2015 Article Accepted on 01/11/2015
INTRODUCTION
Arterial blood gas analysis is a routine and important
procedure in emergency and intensive care unit in daily
practice specially for ventilator patients and for patients
having cardiopulmonary compromise. Arterial blood
sample can be used to measure acid-base balance,
electrolytes, gases as well as saturation simultaneously within few minutes.
[1] There are so many factors that
affect the accuracy of blood gas analysis upto 75%,
including preanalytical influences such as skill of
collecting sample, temperature, site of sampling, air in
the syringe, time for analysis, improper mixing, syringe
material, type and concentration of heparin. [2-4]
Heparin influences various parametres of blood gas
analysis that varies from the type of heparin, dry
balanced vs. liquid in the preparation of the sample,
amount of heparin and its mixing with blood sample. [5,6]
Nowadays, preloaded heparin syringes are available in
few centres. But because of non-availability of these
syringes at few places and cost factor in India, residents
and nursing staff are doing blood gas analysis by taking
varies amount of heparin in syringe. We conducted this
study to analyse the effect of heparin amount in sample
on various parameters of blood gas analysis to reduce the
preanalytical errors.
MATERIALS AND METHODS
This prospective observational study was conducted in
the Department of Anaesthesia, A.J. Institute of Medical
Sciences, Mangalore. Informed consent was taken from
all subjects before inclusion in the study. The study was
approved by the Institute Ethics Committee.
Inclusion criteria were 20 healthy adults with age
varying from 20-35 years. Exclusion criteria – subjects
with other significant history of hypertension, renal
disorder, smoking, alcohol, diabetes mellitus, any
respiratory infection, asthma, chronic obstructive
pulmonary disease, metabolic disorders, anemia were not
taken into study. Samples were collected with identical
2-cc glass syringes, using an 24 gauge needle in all the
subjects by well trained nurse. 2 samples were
withdrawn from radial artery in 2ml syringe from each
subject at an interval of 1 hour. In 1 st sample heparin was
flushed completely from the syringe and after that
sample was taken and in 2 nd
sample 0.2ml of heparin was
preloaded and blood was taken from subjects. Both
samples were processed immediately within 5-10min
from arterial blood gas analyzer. All other preanalytical
errors i.e. temperature variation, time lag, air in syringe,
improper mixing, were ruled out. The following
parameters were noted i.e. pH, PO2, PCO2, HCO3, SaO2.
SJIF Impact Factor 2.026
Research Article
ISSN 3294-3211
EJPMR
EUROPEAN JOURNAL OF PHARMACEUTICAL
AND MEDICAL RESEARCH www.ejpmr.com
ejpmr, 2015,2(6), 290-293
*Correspondence for Author: Dr. Ashutosh Kumar Post Graduate, Department of Anaesthesia, A.J. Institute of Medical Sciences and Research Centre, Mangalore 575004.
ABSTRACT
Objectives: To determine the effect of dilution of heparin on several parameters of arterial blood gas analysis in
normal healthy subjects. Methods: We compared arterial blood gas analysis in 2 samples of blood, 1 st glass syringe
flushed with heparin and 2 nd
glass syringe consisted of 0.2ml of heparin collected from 20 healthy subjects.
Results: In the present study in sample-2, we observed a significant increase in the levels of PO2 (208.5±33.6), pH
(7.49±0.039) when compared to sample-1 PO2 (88.85±6.22) and pH (7.4±0.041), with p-value<0.0001 in both. In
sample -2 values of PCO2 (16.17±2.21), HCO3 (12.97±2.09) were significantly low when compared to sample-1
PCO2 (40.26±3.22) and HCO3 (24.55±1.59) with p-value of <0.0001 in both parameters. Values of oxygen saturation were also measured but there was no significant difference. Conclusions: Amount of heparin is an
important variable factor for arterial blood gas analysis sampling. Extra amount of heparin can cause alteration in
pH, PO2, PCO2, HCO3, electrolytes and other parameters. Syringes should be flushed with heparin or should
contain less than 0.1ml of heparin while analysis.
KEYWORDS: Heparin, Arterial blood gas analysis.
Ashutosh et al. European Journal of Pharmaceutical and Medical Research
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291
Statistical analysis was done using the SPSS version 16.0
(NY, USA). Data were expressed as mean ± standard
deviation and were analyzed using Student’s t-test. P
value of <0.05 was considered statistically significant.
RESULTS
The table shows comparison of all parameters i.e. pH,
PO2, PCO2, HCO3, SaO2 between two samples.
Arterial blood gas
parameters Variables
Sample(1) flushed
with heparin
Sample(2) with
0.2ml heparin P value
PO2
mean 88.85 208.5
<0.0001 Standard deviation 6.22 33.6
range 86-92 193-224
PCO2
mean 40.26 16.17
<0.0001 Standard deviation 3.22 2.21
range 39-42 15-17
pH
mean 7.4 7.49
<0.0001 Standard deviation 0.041 0.039
range 7.38-7.42 7.47-7.51
HCO3
mean 24.55 12.97
<0.0001 Standard deviation 1.59 2.09
range 24-25 12-14
SaO2
mean 97.15 97.20 0.91 (Non-
significant) Standard deviation 1.12 1.46
range 96.6-97.7 96.5-97.9
A increase in the pH was observed in sample 2 when
compared to sample 1(Figure-1). Both carbon dioxide
pressure and bicarbonate concentration showed an
inverse relation with the volume of heparin used. There was a close relation between the percentage change in
each set of values for carbon dioxide pressure and actual
bicarbonate concentration from baseline and the
percentage volume of heparin in each sample (Figure-
2,3).
A increase in PO2 was observed in sample 2 (Figure-4),
while there was no significant change in values of
saturation (Figure-5).
COMPARISON OF pH BETWEEN THE GROUPS
S A M
P LE
1
S A M
P LE
2
6.8
7.0
7.2
7.4
7.6
7.8
8.0
p H
Figure-1.
COMPARISON OF PCO2 BETWEEN THE GROUPS
SAMPLE 1 SAMPLE 2 0
10
20
30
40
50
P C
O 2 (
m m
H g
)
Figure-2.
COMPARISON OF HCO3 BETWEEN THE GROUPS
S A M
P L E 1
S A M
P L E 2
0
10
20
30
m E
q /L
Figure-3.
Ashutosh et al. European Journal of Pharmaceutical and Medical Research
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292
COMPARISON OF PO2 BETWEEN THE GROUPS
SA M
PL E
1
SA M
PL E
2
0
100
200
300
P O
2 (m
m H
g )
Figure-4.
COMPARISON OF SPO2 BETWEEN THE GROUPS
S A M
P L E 1
S A M
P L E 2
85
90
95
100
105
% S
A T
U R
A T
IO N
O F
O X
Y G
E N
Figure-5.
DISCUSSION Arterial blood gas analysis is very important mode of
investigation to monitor ventilator patients and sick
patients. This is a routine procedure performed in ICU.
But its accuracy is affected by several factors like post-
draw metabolism, heparin, air bubble, storage,
temperature, transport, abnormal cell count, abnormal
mixing and several other factors.
Heparin, first isolated in 1916 from liver tissue, is a
naturally occurring anticoagulant present in all
mammalian species. [7]
It is synthesized in mast cells and
basophils, and stored in the secretory granules of these cells. Since mast cells are present in many tissue types,
heparin can be sourced from a range of extra-hepatic
tissues. [8]
Commercial preparations are now most
commonly derived from the mucosal intima of pig
(porcine) intestine. The ideal anticoagulant should be
dry, free of interference in laboratory tests, inexpensive
and completely reliable as an anticoagulant. [9]
The
International Federation of Clinical Chemistry
recommend for blood gas sampling, filling up of the dead
space of the syringe with heparin, to lubricate the inner
wall of the syringe, to expel the excess anticoagulant and
to collect at least 20 times the dead space volume of
blood to avoid preanalytical errors. [10,11]
Dry balanced
heparin is “electrolyte balanced,” (containing Lithium
and Zinc rather than sodium or calcium) to prevent
interference with the numerous electrolytes and other
parameters estimated. [12,13]
A variety of heparin salts, in either liquid or lyophilized form, have been used as
anticoagulants. Lithium heparin, the most commonly
used anticoagulant, induces a negative bias in the
measurement of ionized calcium concentration. [14]
Heparin is acidic and lowers pH. Heparin of lower
strength (1000 instead of 5000 units per ml) or heplock
solution should be used. Small volume of heparinised
saline just for lubricating the syringe and plunger should
be used. If volume is more, dissolved oxygen in
heparinised saline may increase PaO2.The principle
disadvantage of liquid heparin is a potential for error if
blood is over-diluted with heparin. This potential error is due to the considerable difference in pH, pCO2, and pO2
of liquid heparin compared with that of arterial blood. [15]
Approximate values for heparin solution are pH 6.4;
pCO2, 7.5 mmHg (1kPa), and pO2, 160 mmHg (21kPa),
reflecting the fact that heparin is an acidic solution in
equilibrium with air. [16,17]
Heparin has two different effects on blood gas samples
based on its intrinsic chemical properties and dilution of
the sample. As heparin dilutes mainly the plasma phase
of the blood sample the magnitude of the dilution of a 1 ml blood sample by 0.05 ml of liquid heparin may be
around 10%. Siggaard Andersen found a fall in Pco2 of
16% when blood was diluted by 12-13% with saline.
When adding dry heparin to concentrations of 2, 4 and
10 mg/ml, Siggaard Andersen found that the average
effect of 1 mg heparin per ml blood was +0.1 mmHg
Pco2. [18]
In contrast, Bradley et al. reported a 28% fall in
Pco2, at the same dilution. [19]
Few studies have suggested that measured pH is resistant
to dilution of heparin, even if heparin and blood are
mixed in equal volumes (i.e.,50% dilution of blood), presumably due to the buffering capacity of blood. In
some studies, no effect on pO2 was observed, while in
others, an increase in pO2 was observed at high (35% to
50%) dilution. pCO2 is the most susceptible parameter.
As long as dilution is less than 10% (e.g., 0.5 mL heparin
added to 5.0 mL of blood), pCO2 is not significantly
affected, but dilutions above 10% are associated with
significant decline in pCO2 values. There is an
approximate 1% decline in pCO2 for every 1% increase
in dilution. Calculated acid-base parameters, bicarbonate,
and base excess that are derived from measured pCO2 are affected to the same magnitude.
[20-22]
Previous studies suggest that heparin dilution also affects
Na+, K + and ionic calcium varying from − 12% to 12%.
Various authors have previously shown that estimation
of Na+, K + and Ca2 + may be low in a sample collected
for and analyzed by the blood gas machine. This has
previously been attributed to binding of cations from the
Ashutosh et al. European Journal of Pharmaceutical and Medical Research
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sample by liquid heparin. [23-25]
Previous studies are also
supportive of the fact that arterial blood sample should
be collected in appropriate conditions with minimal
amount of heparin and other prerequisite conditions to be
followed, for accurate report. [26,27]
CONCLUSION
We recommend that no more than 0.1 cc of heparin to be
use in the syringe for arterial blood drawn or to flush the
syringe with heparin is sufficient as it will alter all
parameters. It is desirable to collect sample anaerobically
and use a glass syringe as plastic syringes are permeable
to air. The sample should be processed immediately,
preferably within 30 minutes because cells consume
oxygen and produce CO2. PaO2 varies with dilution and
can be increased also giving misconception of good
ventilation.
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